1. Field of the Invention
The present invention relates to power management in computer systems.
2. Background of the Related Art
The power consumed by a computer system represents a significant portion of the operational cost of that system. The cost of powering a computer system represents a significant portion of the overall ownership expense. The cost of cooling a computer system is another significant cost component, because computer systems generate heat in relation to the amount of power consumed, and because sufficient cooling infrastructure must be provided to cool the system. Such costs are particularly sizeable in a datacenter, which may include as many as tens of hundreds of high-power, rack-mounted servers mounted in multiple, high-density chassis or racks. Therefore, power management is an important consideration in the design, development, and operation of computer systems.
Power in a computer system is commonly managed on multiple levels. In a datacenter, for example, the total power allotted to the entire datacenter may fluctuate according to time-varying energy costs. The power allotted to the datacenter may be subdivided among multiple racks and among the rack-mounted chassis in the datacenter. Power to the servers within a particular chassis may be managed using a management module shared by the servers in that chassis, for example by establishing a variable power cap may be enforced upon each server. The server power caps may be individually varied by the management module to satisfy the demands placed on each server, while keeping power consumption within the power limit set for the chassis. Within a particular server, power to individual devices may be managed by the operating system to optimize power consumption, such as to reduce power consumption to idle devices.
Power management includes both hardware and software aspects. The amount of power used by system devices may be controlled “in-band,” “out-of-band,” or a combination thereof. By definition, in-band methods are implemented by the operating system (OS), while out-of-band methods are implemented by the platform, bypassing the OS. For example, a system configured according to the standardized Advanced Configuration and Power Interface (ACPI) specification may be managed out-of-band by a Baseboard Management Controller (BMC) or managed in-band according to Operating System-directed configuration and Power Management (OSPM).